Technical Field
The present disclosure relates to augmented reality, and more specifically to techniques for capturing accurate information describing the location of subsurface features usable in providing an augmented reality view.
Background Information
Excavation work (e.g., road excavation work) often creates traffic disruptions that inconvenience local residents and harm the local economy. Further, there is potential of injury should mistakes occur. Accordingly, it is important to carefully plan such work, so that it can be conducted efficiently and safely. Traditionally, excavation work has been planned in the field using paper plans, where a worker looks at the plans and the physical environment (e.g., the road surface), and manually determines where subsurface features (e.g., subsurface utilities such as water pipes, sewer pipes, electrical conduits, etc.) are located. More recently, there has been research into using augmented reality for excavation work, to permit a worker to see a computer-generated visualization of subsurface features imposed upon a view of the physical environment.
In a typical adaptation of augmented reality technology to excavation work, a worker may hold or wear an augmented reality device, such as a head-mounted display unit (e.g., the Microsoft HoloLens® head-mounted display unit). An augmented reality application executing on the device uses a camera to capture a stream of images of the physical environment. A pose determination system (e.g., a number of position and orientation sensors and supporting software) determines the pose of the camera. Based on the pose, the application aligns information that describes subsurface features (e.g., a 3-D model, a 2-D map or drawing, etc.) with the images of the physical environment, and augments the images of the physical environment based thereon. In some implementations, the augmentations take the form of renderings of subsurface features at their actual locations made visible via a virtual excavation in the terrain surface. In other implementations, the augmentations take the form of virtual paint markings upon the terrain surface (e.g., the road surface) generated from projections from the locations of subsurface features. A wide variety of other augmentations are also possible. Regardless, for the augmentations to be meaningful, they must be based on accurate information describing the locations of subsurface features. If the locations are unreliable, the augmentations cannot be trusted.
Unfortunately, accurate information describing the locations of subsurface features is typically scarce. Older maps and drawings of existing utility networks may lack necessary detail, and may not reflect in-field changes made to the network. Even drawings for new utility networks signed off by engineers in the field often do not show the true locations of the subsurface utilities. Typically, this is because no one precisely determines the locations where subsurface utilities are actually installed. Ideally, to precisely determine locations a survey is conducted by survey personnel. However, having survey personal on-site to conduct these surveys adds expense, and generally is not standard practice for new construction in many areas.
Determining the precise locations of older subsurface features (e.g., subsurface utilities) can be even more burdensome. Subsurface features are typically hidden from view, and only revealed through excavation work. A comprehensive survey of an existing utility network typically would require a massive amount of excavation (e.g., many entire streets being dug up), which would be very expensive and otherwise impractical.
Portions of existing utility networks are often revealed for short periods of time during routine maintenance or repair work, being excavated and then reburied shortly thereafter when the maintenance/repair is complete. During the brief time window when the utilities are visible they theoretically could be surveyed. Even though only a very small portion of the entire network is revealed at any given time, a series of partial surveys could progressively improve the accuracy of available location information. However, having survey personal ready for conducting such surveys would be quite expensive. Excavation workers typically do not know the exact times subsurface utilities will become visible. Survey personnel would therefore have to be always on-site, available at a minutes notice, so as to not slow down the progress of the maintenance/repair work. Due to these burdens, partial surveys are rarely conducted in practice.
Other techniques could potentially be tried to precisely determine the locations of new or exiting subsurface features (e.g., subsurface utilities). For example, during an excavation, when a subsurface feature is visible, a laser scanner could be used. However, techniques involving a laser scanner suffer from similar disadvantages to techniques involving survey equipment. Laser scanners typically require specialized personnel to operate, and these personnel (like survey personnel) would have to be always on-site, adding expense and hindering new construction or maintenance/repair workflow. Further, laser scanners themselves are quite expensive.
Indirect measurement techniques could be attempted that do not require excavation. For example, techniques involving ground penetrating radar, electromagnetic sensors or inferences based on surface features (e.g., inferring sewer pipe locations from manhole covers in a road, etc.) could be attempted. However, such techniques also suffer shortcomings. Techniques based on ground penetrating radar or electromagnetic sensors may not be suited for all types of soil and may have depth limitations. Further, they typically require specialized personnel and expensive equipment. Further, techniques based on inferences generally cannot provide the level of accuracy desired.
Accordingly, there is a need for new techniques for capturing accurate information describing the locations of subsurface features (e.g., subsurface utilities) that could be used to enable augmented reality. Preferably, such techniques would not require specialized personnel, and would be low cost, such that they could be widely integrated into typical excavation workflows.